Input power appraisal based wireless power system

ABSTRACT

A wireless power system (WPS) has a wireless power transmitter (WPT) that appraises an input power available to a power inverter from one or more input power sources. The WPT comprises the power inverter that wirelessly transmits power to a wireless power receiver (WCR) of the WPS, and a power appraiser circuit (PAC). The PAC ascertains maximum input power available to the power inverter from the input power sources. The PAC includes a variable load connected to a path carrying the input power to the power inverter or one or more input pins that receive power ratings of the input power sources that indicate available maximum input power from the input power sources. The ascertaining of maximum input power available to the power inverter from the input power sources appraises the input power available to the power inverter. The WCR receives information representing maximum power deliverable by the WPT.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.13/950,288 filed in the United States Patent and Trademark Office onJul. 25, 2013 which claims benefit from U.S. Provisional Application No.61/676,916 filed on Jul. 28, 2012.

BACKGROUND

In practical day-to-day wireless charging, there are scenarios where thewireless power transmitter cannot satisfy the power needs of one or morewireless power receivers that are placed on top or in the vicinity of itbecause of limitations of its input power source. For example, awireless power transmitter connected to a USB 2.0 port can only draw 2.5Watts (W) of power from the USB port. A wireless power receiver,external or integrated into an end device such as a smartphone, tablet,etc., may be positioned on top of such a wireless power transmitter toreceiver power wirelessly from the wireless power transmitter to chargethe end device. During charging, if the wireless power receiver startsdrawing (say) 3 W of power, then a system reset will occur as thewireless power receiver's needs cannot be satisfied by the wirelesspower transmitter which has only 2.5 Watts (W) of power at its disposalfrom its input power source, the USB 2.0 port. On recovery from reset,the same system behavior repeats—the system resets repeatedly and thewireless power receiver fails to charge the end device. Battery chargingof the end device will repeatedly start and stop which has an adverseeffect on the reliability and life of the battery. The user experiencewill be unpleasant and the consumer may steer away from wirelesscharging as they may not recognize what is causing such an unstablebehavior. Besides, there are multiple USB standards, for example, USB1.0, USB 2.0, and USB 3.0 and each has its own maximum power rating.Depending on the type of USB port, the power rating can vary from 0.5 W,2.5 W, 4.5 W, etc. As a result, the consumer may be confused andfrustrated with varying wireless charging behavior and performancedepending on the USB port type into which the wireless power transmitteris plugged in.

Wireless power transfer must be stable for a good end user experience asthe stability of the power transfer directly impacts charging time,battery reliability, battery lifetime, etc. The wireless power transferbecomes unstable whenever the wireless power transmitter, by virtue ofthe limitations of input power source(s), is unable to satisfy thesimultaneous dynamic power needs of one or more wireless power receiversplaced on top or in the vicinity of the wireless power transmitter.Hence, there is a long felt but unresolved need for a wireless powercharging system that overcomes such an unstable power transfer behavior.

SUMMARY OF THE INVENTION

An input power appraisal based wireless power system comprising awireless power transmitter that appraises an input power available toits power inverter from one or more of multiple input power sources isprovided. The wireless power system disclosed herein overcomes unstablepower transfer behavior between the wireless power transmitter and thewireless power receiver by determining the maximum power available fromeach of its one or more of multiple input power sources and thennegotiating a sustainable power transfer contract with a wireless powerreceiver before entering a full power transfer phase. The wireless powertransmitter appraises maximum available input power and negotiates apower transfer contract with the wireless power receiver to avoid anunstable power transfer. The wireless power transmitter disclosed hereincomprises the power inverter and a power appraiser circuit. The powerinverter is configured to wirelessly transmit power to the wirelesspower receiver of the wireless power system. The power invertercomprises a switch network, a variable matching circuit, a control logiccircuit, an ADC, a demodulator circuit and a wireless power transmitinterface. The power appraiser circuit is configured to ascertainmaximum input power available to the power inverter from the input powersources. The power appraiser circuit comprises a register unit thatstores a value indicating the ascertained maximum input power availableto the power inverter from each of the power sources. The powerappraiser circuit ascertains maximum input power available to the powerinverter via a variable load connected to a path carrying the inputpower to the power inverter. The variable load is configured to varyload characteristic of the path carrying the input power to the powerinverter. In an embodiment, a regulator or a switch is operably coupledto the variable load connected to the path carrying the input power tothe power inverter. In another embodiment, the power appraiser circuitdetermines the available maximum input power from the input powersources via one or more input pins configured to receive power ratingsof the input power sources. In one approach, the pins are configuredwith an analog voltage. The power appraiser circuit senses the analogvoltage with its ADC and translates that analog voltage to a maximuminput power rating via a lookup table, an algorithm, etc. In anotherapproach, the wireless power transmitter interprets and decodes the pinsas digital logic levels to ascertain the maximum input power rating ofthe input power sources. In the third approach, an external controllerprograms the power appraiser circuit's register unit with the maximumpower ratings of the input power sources via those input pins.Ascertaining the maximum input power available to the power inverterfrom the input power sources appraises the input power available to thepower inverter.

At startup, when the wireless power receiver receives initial power, thewireless power receiver provides configuration information such as itsmaximum output power limit, input power threshold to deliver thatmaximum output power, etc., via a communication link to the wirelesspower transmitter. Configuration information such as maximum outputpower limit and input power threshold represent requirements of thewireless power receiver for the wireless power receiver to operate atits full potential. The wireless power transmitter uses the storedvalues in the register unit of the power appraiser circuit to select theinput power source that can deliver to these requirements of thewireless power receiver. In the first embodiment, the wireless powertransmitter selects an input source that satisfies the maximum outputpower limit of the wireless power receiver. The wireless powertransmitter estimates the efficiency of the wireless power system basedon its internal configuration information and/or the configurationinformation from the wireless power receiver. Based on this estimatedefficiency and available maximum power of each of the power sources thatis stored in the register unit of the power appraiser circuit, thewireless power transmitter selects the input power source(s) thatsatisfies or is closest to satisfying the maximum output power limitrequirement of the wireless power receiver. In the second embodiment,the wireless power transmitter selects an input source that satisfiesthe input power threshold of the wireless power receiver. In thisembodiment, the wireless power transmitter does not estimate theefficiency of the wireless power system. Instead, it estimates its ownoperating efficiency in conjunction with the wireless power receiverbased on its internal configuration information and/or the configurationinformation from the wireless power receiver. Based on this estimatedefficiency and available maximum power of each of the power sources thatis stored in the register unit of the power appraiser circuit, thewireless power transmitter selects the input power source(s) thatsatisfies or is closest to satisfying the input power thresholdrequirement of the wireless power receiver. If multiple input sourcessatisfy the wireless power receiver requirement, then the wireless powertransmitter selects among the eligible input power sources based ofother criteria such as safety. If none of the input sources satisfy thewireless power receiver requirement, then the wireless power transmitterselects the input power source that is closest to satisfying therequirement. Having selected the input power source, the wireless powertransmitter sends a message to the wireless power receiver.

The input power appraisal based wireless power system further comprisesa wireless power receiver configured to receive an information messagefrom the wireless power transmitter. In the first embodiment, theinformation message represents the maximum power that the wireless powerreceiver can deliver to its load. In the second embodiment, theinformation message represents the maximum power that the wireless powertransmitter can deliver to the wireless power receiver. In the secondembodiment, based on the information message, the wireless powerreceiver applies its algorithms to compute the maximum amount of powerthat it can deliver to its load. The maximum output power limitrepresents the maximum amount of power that the wireless power receivercan deliver to its load. The wireless power receiver reconfigures itspower output circuitry to deliver power at or below this maximum outputpower limit. The power output circuitry is reconfigured by multiplemethods, for example, by adjusting a current limit in regulators orcharge management controller operably disposed in the wireless powerreceiver, limiting a feedback voltage or a duty cycle in the regulators,physically limiting a load operably disposed at the output of thewireless power receiver, etc. The reconfigured power output circuitrydelivers power to the load up to the maximum output power limit. In anembodiment, a downstream active load such as a charge managementcontroller is operably coupled to the output of the wireless powerreceiver disclosed herein. In such a case, the wireless power receiversuitably configures the downstream active load to draw power notexceeding the maximum output power limit of the wireless power receiver.

Disclosed herein is also a method for establishing an optimal powertransfer process from the wireless power transmitter to the wirelesspower receiver. The power appraiser circuit in the wireless powertransmitter appraises maximum power capability of each of the inputpower sources. The wireless power transmitter detects a wireless powerreceiver proximal to the wireless power transmitter. On detection of thewireless power receiver, the wireless power transmitter transmits aminimum power to the wireless power receiver for powering the wirelesspower receiver and initiating communication with the wireless powertransmitter. Once powered-up, the wireless power receiver communicatesconfiguration information to the wireless power transmitter via acommunication link established between the wireless power transmitterand the wireless power receiver.

The wireless power transmitter is aware of the maximum output powerlimit of the wireless power receiver from the configuration informationshared by wireless power receiver. The wireless power transmitter checksthe power ratings of the input power sources to identify an input powersource that provides sufficient power to the wireless power system toallow the wireless power receiver to deliver power to its load up to itsmaximum output power limit. On successful identification of such aninput power source, the wireless power transmitter transmits aninformation message indicating the successful match to the wirelesspower receiver; on receiving this message, the wireless power receiverstarts drawing and delivering power up to the configured maximum outputpower limit. If none of the input power sources can provide sufficientpower into the wireless power system, then the wireless powertransmitter selects the best input power source that comes closest tosatisfying the requirement. Based on the maximum power available fromthe selected input power source, the wireless power transmitter computesthe maximum power deliverable by the wireless power receiver to itsload. The wireless power transmitter transmits an information messagecontaining this maximum power value to the wireless power receiver. Thewireless power receiver reconfigures the maximum power limit of itspower output circuitry to comply with this maximum power value containedin the information message from the wireless power transmitter. Aftercompletion of power output circuitry reconfiguration, the wireless powerreceiver sends an acknowledgement message to the wireless powertransmitter. On receiving the acknowledgement, the wireless powertransmitter transmits an information message indicating to the wirelesspower receiver that it can start delivering power within thereconfigured maximum power limit thereby establishing a stable andoptimal power transfer phase.

In an embodiment, the wireless power transmitter is aware of the inputpower threshold of the wireless power receiver from the configurationinformation shared by wireless power receiver. The input power thresholdrepresents the amount of power that the wireless power receiver needs toreceive from the wireless power transmitter for the wireless powerreceiver to deliver its configured maximum output power to itsdownstream passive or active load. The wireless power transmitter checksthe power ratings of the input power sources to identify an input powersource that provides sufficient power to allow the wireless powertransmitter to deliver power to the wireless power receiver in excess ofthe wireless power receiver's input power threshold. On successfulidentification of such an input power source, the wireless powertransmitter transmits an information message indicating the successfulmatch to the wireless power receiver; on receiving this message, thewireless power receiver starts drawing and delivering power up to theconfigured maximum output power limit. If none of the input powersources can provide sufficient power into the wireless power system,then the wireless power transmitter selects the best input power sourcethat comes closest to satisfying the input power threshold requirement.Based on the maximum power available from the selected input powersource, the wireless power transmitter computes the maximum power thatit can deliver to the wireless power receiver. The wireless powertransmitter transmits an information message containing this maximuminput power value to the wireless power receiver. The wireless powerreceiver computes its maximum output power limit based of the maximuminput power value from the information message. The wireless powerreceiver reconfigures its maximum output power limit of its power outputcircuitry to comply with this computed maximum power value. Aftercompletion of power output circuitry reconfiguration, the wireless powerreceiver sends an acknowledgement message to the wireless powertransmitter. On receiving the acknowledgement, the wireless powertransmitter transmits an information message indicating to the wirelesspower receiver that it can start delivering power within thereconfigured maximum power limit thereby establishing a stable andoptimal power transfer phase.

For a period of time following the start of power transfer, the wirelesspower transmitter actively monitors for unstable power transferbehavior. Depending on various factors such as operating efficiency ofthe wireless power transmitter and wireless power receiver, positionalalignment between the wireless power transmitter's transmit powerinterface and the wireless receiver's receive power interface, etc., theselected input power source may not yet be able to source sufficientpower into the wireless power system for the wireless power receiver todeliver its configured maximum output power to its downstream passive oractive load. If there is an unstable power transfer behavior, thewireless power transmitter suitably reduces its efficiency estimates inevery pass to yield maximum output power limit and input power thresholdvalues that are lower than those values computed and communicated in theprevious pass. With this approach, if ever there were any unstable powertransfer behavior, the wireless power transmitter will trap andeliminate such an unstable power transfer behavior right in the initialperiod of charging. The wireless power system overcomes unstable powertransfer behavior by computing, configuring and fine-tuning asustainable maximum output power limit of the wireless power receiverbased of the maximum available power from the wireless powertransmitter's input power sources.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe invention, is better understood when read in conjunction with theappended drawings. For the purpose of illustrating the invention,exemplary constructions of the invention are shown in the drawings.However, the invention is not limited to the specific methods andcomponents disclosed herein.

FIG. 1A exemplarily illustrates a schematic diagram of a power appraisalbased wireless power charging system, where inductive coupling is usedto transmit wireless power through a magnetic field.

FIG. 1B exemplarily illustrates an embodiment of the power appraisalbased wireless power charging system, where capacitive coupling is usedto transmit wireless power through an electric field.

FIG. 2A exemplarily illustrates a first embodiment of the powerappraiser circuit of the power appraisal based wireless powertransmitter.

FIG. 2B exemplarily illustrates a second embodiment of the powerappraiser circuit of the power appraisal based wireless powertransmitter.

FIG. 2C exemplarily illustrates a third embodiment of the powerappraiser circuit of the power appraisal based wireless powertransmitter.

FIG. 2D exemplarily illustrates a fourth embodiment of the powerappraiser circuit of the power appraisal based wireless powertransmitter.

FIG. 3 exemplarily illustrates a graphical representation showing avariation in an input voltage and an input current as a load is variedin the power appraiser circuit.

FIG. 4 exemplarily illustrates a flow chart comprising the steps forestablishing a stable and optimal power transfer from the wireless powertransmitter to the wireless power receiver.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A exemplarily illustrates a schematic diagram of an input powerappraisal based wireless power charging system 100, where inductivecoupling is used to transmit wireless power through a magnetic field.The input power appraisal based wireless power charging system 100disclosed herein comprises a wireless power transmitter 100 a and awireless power receiver 100 b. The wireless power transmitter 100 acharges the wireless power receiver 100 b. The wireless powertransmitter 100 a disclosed herein comprises a power inverter, and apower appraiser circuit 109 exemplarily illustrated as a “powerappraiser unit” in FIGS. 1A-1B and FIGS. 2A-2D. The wireless powertransmitter 100 a is configured to appraise an input power available tothe power inverter from one or more of multiple input power sources. Thepower inverter comprises a switch network 102 exemplarily illustrated inFIGS. 1A-1B, a variable matching circuit 103 exemplarily illustrated asa “Zmatch” block in FIGS. 1A-1B, a control logic circuit 104 exemplarilyillustrated in FIGS. 1A-1B and FIGS. 2A-2D, a transmit power interface107 exemplarily illustrated in FIGS. 1A-1B, an ADC circuit 105exemplarily illustrated in FIGS. 1A-1B and FIGS. 2A-2B and amodulator/demodulator circuit 106 exemplarily illustrated in FIGS.1A-1B. The variable matching circuit 103 comprises one or more ofpassive electronic components, for example, a resistor, a capacitor, amagnetic device, a transducer, a transformer, etc.; active electroniccomponents, for example, a diode, a transistor such as a metal oxidesemiconductor field effect transistor (MOSFET), a bipolar transistor,etc., operational amplifiers, an optoelectronic device, etc., andelectronic switches. These electronic components in combination areutilized to vary impedance of the wireless power transmitter 100 a priorto transmitting power to the wireless power receiver 100 b.

The switch network 102 is configured to receive an input power andvoltage 101 from the power appraiser circuit 109. The variable matchingcircuit 103 is connected between the switch network 102 and thetransmitter power interface 107. In FIG. 1A, the wireless powertransmitted to the wireless power receiver 100 b is magnetic field basedusing inductive coupling. The transmitter power interface 107 is atransmitter coil that is configured to wirelessly transmit power to thewireless power receiver 100 b. The transmitter coil 107 is used forinducing a magnetic field to a coupling region for providing energytransfer to the wireless power receiver 100 b. The wireless powertransmitter 100 a transmits power to the wireless power receiver 100 bby emanating the magnetic field using the transmitter coil 107. Thewireless power receiver 100 b comprises a receiver coil 108 that picksup the magnetic field with a certain coupling coefficient that existsbetween the transmitter coil 107 and the receiver coil 108.

The control logic circuit 104 is configured to provide a pulse widthmodulated (PWM) signal to the switch network 102 to operate the switchnetwork 102 in a frequency regime and/or a duty cycle regime. Analoginput signals are converted to digital signals by an analog to digitalconverter (ADC) 105 operably coupled to the control logic circuit 104 ofthe wireless power transmitter 100 a. The output signal of the ADC 105is fed to the control logic circuit 104. The modulator/demodulator block106 senses, filters and decodes messages from the wireless powerreceiver 100 b. The output of the modulator/demodulator block 106 isalso fed to the control logic circuit 104. The control logic circuit 104sends another PWM signal to the modulator/demodulator block 106 for acommunication link that exists from the wireless power transmitter 100 ato wireless power receiver 100 b. The control logic circuit 104 enablesor disables electronic components in the variable matching circuit 103using general purpose input/outputs (GPIOs) and switches. The switchnetwork 102 comprises transistors that are configured to change a state,for example, into an on state or an off state, based on the PWM signalsupplied to the switch network 102.

FIG. 1B exemplarily illustrates an embodiment of the input powerappraisal based wireless power system 100, where capacitive coupling isused to transmit wireless power through an electric field. The wirelesspower transmitter 100 a comprises a power inverter and a power appraisercircuit 109 as disclosed in the detailed description of FIG. 1A. In thisembodiment, the power inverter's transmit power interface 107 comprisesof one or more capacitors. The power inverter also comprises of a switchnetwork 102, a variable matching circuit 103, a control logic circuit104, an ADC circuit 105 and a modulator/demodulator circuit 106 asdisclosed in the detailed description of FIG. 1A. The variable matchingcircuit 103 is connected between the switch network 102 and the one ormore capacitors of the transmit power interface 107 of the wirelesspower transmitter 100 a. The wireless power transmitted to the wirelesspower receiver 100 b is electric field based using capacitive couplingexisting between the capacitor(s) 107 of the wireless power transmitter100 a and the capacitor(s) 111 of the wireless power receiver 100 b. Thecapacitor(s) 107 of the wireless power transmitter 100 a is configuredto wirelessly transmit power to the wireless power receiver 100 b. Thecapacitor(s) 107 is used for inducing an electric field to a couplingregion for providing energy transfer to the wireless power receiver 100b. The wireless power transmitter 100 a transmits power to the wirelesspower receiver 100 b by emanating the electric field using the capacitor107. The capacitor(s) 111 of the wireless power receiver 100 b picks upthe electric field with a certain coupling coefficient that existsbetween the capacitor(s) 107 of the wireless power transmitter 100 a andthe capacitor(s) 111 of the wireless power receiver 100 b.

The power appraiser circuit 109 is configured to ascertain maximum inputpower available to the power inverter by quantifying the maximumavailable input power to the power inverter from multiple input powersources. Ascertaining the maximum input power available to the powerinverter from the input power sources appraises the input poweravailable to the power inverter. Consider an example where the wirelesspower transmitter 100 a is powered up from an input power source of anunknown type and the input power is initially applied to the wirelesspower transmitter 100 a. When the input power is initially applied tothe wireless power transmitter 100 a, the power appraiser circuit 109engages and determines the maximum input power available from that powersource. The wireless power transmitter 100 a switches among itsdifferent input power sources using a “make-before-break” switchingtechnique. The “make-before-break” switching technique refers to aconfiguration in the wireless power transmitter 100 a where a newconnection path is established before any previous contacts are opened.The power appraiser unit determines the maximum input power availablefrom each of the power sources.

FIG. 2A exemplarily illustrates a first embodiment of the powerappraiser circuit 109 of the wireless power transmitter 100 a. The powerappraiser circuit 109 is exemplarily illustrated as a “power appraiserunit” in FIG. 2A. The power appraiser circuit 109 has a variable load203 exemplarily illustrated as “R_(LOAD)” in FIGS. 2A-2B that iscontrolled by a control logic circuit 104, for example, a state machine,a microcontroller, etc. The variable load 203 is connected to a pathcarrying the input power to the power inverter. The variable load 203 isconfigured to vary load characteristics of this path. The variable loadR_(LOAD) 203 can be implemented, for example, using resistors, MOSFETs,transistors such as bipolar transistors, duty cycle varied switching,etc. The power appraiser circuit 109 determines the maximum input poweravailable to the power inverter by varying the R_(LOAD) 203 from a highresistance to a low resistance while monitoring the input power which isa product of I_(IN) and V_(IN) sourced from an adaptor. The powerappraiser circuit 109 stores a value indicating the maximum input poweravailable from the input power source to the power inverter in aregister unit 202, for example, a memory unit. For example, the powerappraiser circuit 109, by varying R_(LOAD) 203 between 1 Kilo ohms and 1ohm, may recognize that the maximum input current that it can draw froman input source of 5 Volts is 1 Ampere. In such a case, the powerappraiser circuit 109 would program the register unit 202 elementcorresponding to the input source with a value of 5 corresponding to 5Watts.

FIG. 2B exemplarily illustrates a second embodiment of the powerappraiser circuit 109 of the power appraisal based wireless powertransmitter 100 a. The power appraiser circuit 109 is exemplarilyillustrated as a “power appraiser unit” in FIG. 2B. The power appraiserunit has a variable load 203 exemplarily illustrated as “R_(LOAD)” inFIGS. 2A-2B, that is controlled by a logic circuit 201, for example, astate machine, a microcontroller, etc. The power appraisal is performedby having an intermediate stage, for example, a regulator or a switch204 before the point of observation, that is the maximum input poweravailable to the power inverter is measured after regulator or a switch204. The regulator or the switch 204 is operably coupled to the variableload 203 connected to the path carrying the input power to the powerinverter. The regulator maintains a constant input voltage to thevariable load 203 and the switch 204 is used to configure a path for theflow of input current. The power appraiser circuit 109 determines themaximum input power available to the power inverter by varying theR_(LOAD) 203, from a high resistance to a low resistance whilemonitoring the input power which is a product of I_(IN), and V_(IN)sourced from an adaptor.

FIG. 2C exemplarily illustrates a third embodiment of the powerappraiser circuit 109 of the power appraisal based wireless powertransmitter 100 a. The power appraiser circuit 109 is exemplarilyillustrated as a “power appraiser unit” in FIG. 2C. One or more inputpins of the power appraiser circuit 109 is configured to receive powerratings of the input power sources that indicate the maximum availablepower from the input power sources. In the first approach, the powerappraisal is performed on the basis of an explicit indication on aseparate pin. For example, if the input pin is at a 3.3V TTL logic level1 (>2.2 Volts), then the maximum available power of the power sourceassociated with the pin may be considered as 10 Watts. If the same inputpin was at a 3.3V TTL logic level 0 of (<1.2 Volts), then the maximumavailable power of the power source associated with the pin may beconsidered to be 5 Watts. In the second approach, the power appraisal isperformed on the basis of decoding the logic levels on multiple inputpins associated with the power source. For example, if pinA and pinB areconfigured with the power rating of the input source X, then if pinA andpinB were both at 3.3V TTL logic level 1 (>2.2 Volts), then the maximumavailable power of the power source X may be considered 30 W. If pinAand pinB were both at 3.3V TTL logic level 0 (<1.2 Volts), then themaximum available power of the power source X may be considered 3 W. IfpinA were at 3.3V TTL logic level 0 and pinB were at 3.3V TTL logiclevel 1, then the maximum available power of the power source X may beconsidered 15 W. In the third approach, the maximum available power ofthe power source(s) is learnt via information provided on the pins by anexternal controller (not shown) following a protocol such as I2C, SPI,etc. In this approach, the pins may be bi-directional carryinginformation-requests and information-responses between Control Logic 104and the external controller. In an embodiment of this approach, powerappraisal is initiated by the Control Logic 104 sending a request forthe power rating information. The request is as per the protocolimplemented on the pins. On receiving the request, the externalmicrocontroller responds with the power rating information. The responseis as per the protocol implemented on the pins. The Control Logic 104extracts the maximum available power values of the input source(s) fromthe response and stores them in the register unit 202 of the powerappraiser circuit 109.

FIG. 2D exemplarily illustrates a fourth embodiment of the powerappraiser circuit 109 of the power appraisal based wireless powertransmitter 100 a. The power appraiser circuit 109 is exemplarilyillustrated as a “power appraiser unit” in FIG. 2D. One or more inputpins of the power appraiser circuit 109 is configured to receive powerratings of the input power sources that indicate the maximum availablepower from the input power sources. In this embodiment, the input pinsare configured with an analog voltage. Power appraisal is performed byADC 105 sensing the analog voltage and Control Logic 104 translating thedigital output of the ADC 105 to the power rating of the input sourcevia a lookup table, an algorithm, etc. For example, if the analogvoltage on the input pin was 1.6V, the ADC 105 may generate a digitalcode (say)0x0F which the Control Logic 104 looks up in its memory todetermine the maximum available power of the power source as 16 Watts.

FIG. 3 exemplarily illustrates a graphical representation showing avariation in an input voltage and an input current as a load is variedin the power appraiser circuit 109. The maximum input power available tothe power inverter, P_(IN, MAX) is approximated to be a product ofI_(IN, MAX) and V_(IN, MIN,) that is I_(IN, MAX)*V_(IN, MIN).

At startup, when the wireless power receiver 100 b receives initialpower, the wireless power receiver 100 b provides configurationinformation such as its maximum output power limit, input powerthreshold to deliver that maximum output power, etc., via acommunication link to the wireless power transmitter 100 a.Configuration information such as maximum output power limit and inputpower threshold represent requirements of the wireless power receiver100 b for the wireless power receiver 100 b to operate at its fullpotential. The wireless power transmitter 100 a uses the stored valuesin the register unit 202 of the power appraiser circuit 109 to selectthe input power source that can deliver to these requirements of thewireless power receiver 100 b. In the first embodiment, the wirelesspower transmitter 100 a selects an input source that satisfies themaximum output power limit of the wireless power receiver 100 b. Thewireless power transmitter 100 a estimates the efficiency of thewireless power system based on its internal configuration informationand/or the configuration information from the wireless power receiver100 b. Based on this estimated efficiency and available maximum power ofeach of the power sources that is stored in the register unit 202 of thepower appraiser circuit 109, the wireless power transmitter 100 aselects the input power source(s) that satisfies or is closest tosatisfying the maximum output power limit requirement of the wirelesspower receiver 100 b. For example, if the estimated system efficiency is50% and maximum output power limit requirement of the wireless powerreceiver 100 b is 5 Watts, then among 3 input power source eachproviding 2.5 Watts, 5 Watts and 10 Watts of power, the wireless powertransmitter 100 a selects the power source that provides 10 Watts asonly that power source can satisfy 50%*10 Watts=5 Watts) the maximumoutput power limit requirement of the wireless power receiver 100 b. Inthe second embodiment, the wireless power transmitter 100 a selects aninput source that satisfies the input power threshold of the wirelesspower receiver 100 b. In this embodiment, the wireless power transmitter100 a does not estimate the efficiency of the wireless power system.Instead, it estimates its own operating efficiency in conjunction withthe wireless power receiver 100 b based on its internal configurationinformation and/or the configuration information from the wireless powerreceiver 100 b. Based on this estimated efficiency and available maximumpower of each of the power sources that is stored in the register unit202 of the power appraiser circuit 109, the wireless power transmitter100 a selects the input power source(s) that satisfies or is closest tosatisfying the input power threshold requirement of the wireless powerreceiver 100 b. For example, if the wireless power transmitter'soperating efficiency is 90% and the input power threshold requirement ofthe wireless power receiver 100 b is 8 Watts, then among 3 input powersource providing 2.5 Watts, 5 Watts and 10 Watts of power each, thewireless power transmitter 100 a selects the power source that provides10 Watts as only that power source can satisfy (90%*10 Watts=9 Watts)the input power threshold requirement of the wireless power receiver 100b. If multiple input sources satisfy the wireless power receiver 100 brequirement, then the wireless power transmitter 100 a selects among theeligible input power sources based of other criteria such as safety. Ifnone of the input sources satisfy the wireless power receiver 100 brequirement, then the wireless power transmitter 100 a selects the inputpower source that is closest to satisfying the requirement. For example,if the wireless power transmitter's operating efficiency is 90% and theinput power threshold requirement of the wireless power receiver 100 bis 5 Watts, then among 2 input power source providing 2.5 Watts and 5Watts of power each, the wireless power transmitter 100 a selects thepower source that provides 5 Watts as that power source is closest(90%*5 Watts=4 Watts) to satisfying the input power thresholdrequirement of the wireless power receiver 100 b. Having selected theinput power source, the wireless power transmitter 100 a sends messageto the wireless power receiver 100 b as per the flow exemplarilydescribed in FIG. 4.

The input power appraisal based wireless power system 100 furthercomprises a wireless power receiver 100 b exemplarily illustrated inFIGS. 1A-1B, configured to receive an information message from thewireless power transmitter 100 a. In the first embodiment, theinformation message represents the maximum power that the wireless powerreceiver 100 b can deliver to its load. In the second embodiment, theinformation message represents the maximum power that the wireless powertransmitter 100 a can deliver to the wireless power receiver 100 b. Inthe second embodiment, based on the information message, the wirelesspower receiver 100 b applies its algorithms to compute the maximumamount of power that it can deliver to its load. The maximum amount ofpower that the wireless power receiver 100 b can deliver to its load isits maximum output power limit. The wireless power receiver 100 breconfigures its power output circuitry to deliver power at or belowthis maximum output power limit. The power output circuitry isreconfigured by multiple methods, for example, by adjusting a currentlimit in regulators 110 or the constant current mode (CC mode) limit ofintegrated charge management controller 110 operably disposed in thewireless power receiver 100 b, limiting a feedback voltage or a dutycycle in the regulators 110, physically limiting a load operablydisposed at the output of the wireless power receiver 100 b, etc. Thereconfigured power output circuitry delivers power to the load up to themaximum output power limit.

In an embodiment, a downstream active load such as a charge managementcontroller or a charge management integrated circuit (CMIC) may beoperably coupled to the output of the wireless power receiver 100 bdisclosed herein. In such a case, the wireless power receiver 100 bsuitably configures the downstream active load to draw power up to themaximum output power limit of the wireless power receiver 100 b. In atypical scenario where a CMIC is drawing power from the wireless powerreceiver 100 b, the wireless power receiver 100 b adjusts the constantcurrent mode (CC mode) limit of CMIC. As an example, if the wirelesspower transmitter 100 a sends the maximum output power limit as 10Watts, then wireless power receiver 100 b with a Voltage Output (Vout)of 10V would program its regulator's current limit and the CMIC's CCmode limit to 1 Ampere. The wireless power receiver 100 b may beconnected to other types of loads, for example, buck, boost, flyback,low-dropout (LDO), etc., and the wireless power receiver 100 bconfigures the load not to draw power beyond the new maximum outputpower limit by adjusting the current limits of these loads, limitingduty cycle of a regulator, limiting a feedback voltage in a feedbackpath of the regulator, etc.

FIG. 4 exemplarily illustrates a flow chart comprising the steps forestablishing a stable and optimal power transfer from the wireless powertransmitter 100 a to the wireless power receiver 100 b shown in FIGS.1A-1B. The power transfer process comprises negotiating a power transfercontract between the wireless power transmitter 100 a and the wirelesspower receiver 100 b to avoid unstable power transfer. The powerappraiser circuit 109 appraises 401 maximum power capability of each ofthe input power sources. At startup, the power appraiser circuit 109 ofthe wireless power transmitter 100 a ascertains the maximum availableinput power as disclosed in the detailed description of FIGS. 2A-2D,from each of the input power sources that are available to the wirelesspower transmitter 100 a to draw power from. The wireless powertransmitter 100 a detects 402 a wireless power receiver 100 b proximalto the wireless power transmitter 100 a. That is, after completion ofthe power appraisal, the wireless power transmitter 100 a checkscontinuously for a wireless power receiver 100 b in its close proximityor environment. The wireless power transmitter 100 a, on detecting thewireless power receiver 100 b, transmits 403 a minimum power to thedetected wireless power receiver 100 b for powering the wireless powerreceiver 100 b and initiating communication with the wireless powertransmitter 100 a. The wireless power receiver 100 b powers up 404 tocommunicate configuration information, for example, wireless chargerreceiver identification, its maximum output power limit, input powerthreshold to deliver that maximum output power, etc., of the wirelesspower receiver 100 b, etc., to the wireless power transmitter 100 a viaa communication link established between the wireless power receiver 100b and the wireless power transmitter 100 a. Configuration informationsuch as maximum output power limit and input power threshold representrequirements of the wireless power receiver 100 b for the wireless powerreceiver 100 b to operate at its full potential. These requirements arehenceforth referred to as optimal operation requirements of the wirelesspower receiver 100 b as satisfying them would enable optimal operationof the wireless power receiver 100 b.

As previously described in the detailed description, the wireless powertransmitter 100 a checks 405 for an input power source whose maximumavailable power satisfies the optimal operation requirement of thewireless power receiver 100 b. The wireless power transmitter 100 acommunicates with the wireless power receiver 100 b based on theidentification. The wireless power transmitter 100 a transmits 406 a “goahead” message or symbol, when an input power source matching theoptimal operation requirements of the wireless power receiver 100 b issuccessfully identified. The “go ahead” message or symbol establishes409 the power contract process and the wireless power receiver 100 bstarts drawing and delivering power to its load. If the input sources donot provide sufficient power to satisfy the wireless power receiver's100 b optimal operation requirement, then the wireless power transmitter100 a selects the input power source that is closest to satisfying theoptimal operation requirement as described previously in the detaileddescription. The wireless power transmitter 100 a sends an update infomessage to the wireless power receiver 100 b containing the newlycomputed sub-optimal but stable operational power limits. On receivingthe message, the wireless power receiver 100 b as described previouslyin the detailed description, may compute the maximum amount of powerthat the wireless power receiver 100 b can deliver to its load. Thewireless power receiver 100 b reconfigures 408 its power outputcircuitry to deliver power at or below this maximum output power limit.It also reconfigures any downstream active loads appropriately to notdraw power in excess of this maximum output power limit. Afterreconfiguration, it sends an acknowledgement message to the wirelesspower transmitter 100 a. On receiving the acknowledgement message, thewireless power transmitter 100 a transmits 406 a “go ahead” message orsymbol. The “go ahead” message or symbol establishes 409 the powercontract process and the wireless power receiver 100 b starts drawingand delivering power to its load.

For a period of time following the start of power transfer, the wirelesspower transmitter actively monitors for unstable power transferbehavior. Depending on various factors such as operating efficiency ofthe wireless power transmitter 100 a and wireless power receiver 100 b,positional alignment between the wireless power transmitter's transmitpower interface and the wireless receiver's receive power interface,etc., the selected input power source may not yet be able to sourcesufficient power into the wireless power system 100 for the wirelesspower receiver 100 b to deliver its configured maximum output power toits downstream passive or active load. This will result in unstablepower transfer behavior. If there is an unstable power transferbehavior, the wireless power transmitter 100 a suitably reduces itsefficiency estimates in every pass to yield maximum output power limitand input power threshold values that are lower than those valuescomputed and communicated in the previous pass. This way, if ever therewere any unstable power transfer behavior, the wireless powertransmitter 100 a traps and eliminates such an unstable power transferbehavior right in the initial period of charging. The wireless powersystem overcomes unstable power transfer behavior by computing,configuring and fine-tuning a sustainable maximum output power limit ofthe wireless power receiver based on its appraisal of the maximumavailable power from the wireless power transmitter's input powersources.

In an embodiment, where the wireless power transmitter 100 a has accessto multiple power domains, for example, inside a computing device suchas a laptop, the power appraiser circuit 109 of the wireless powertransmitter 100 a selects an appropriate input power source that allowsstable power transfer to the wireless power receiver 100 b. The stableand optimal power transfer allows for a good end user experience, as thestability of the power transfer directly impacts charging time, batteryreliability, battery lifetime, etc.

In this wireless power system, the mode of wireless power transfer fromthe wireless power transmitter 100 a to one or more wireless powerreceivers 100 b may be inductive, capacitive or electromagnetic. Thewireless power receivers 100 b may be placed on top or in the vicinityof the wireless power transmitter 100 a. When radio frequency (RF)spectrum such as that used for WiFi is utilized to transfer powerwirelessly from the transmitter to the receiver, the wireless powerreceivers 100 b may be atop, in the vicinity or significantly separatedfrom the wireless power transmitter 100 a. The wireless power system 100aims to overcome unstable power transfer behavior between the wirelesspower transmitter 100 a and one or more wireless power receivers 100 bvia various techniques such as input power source selection,constraining wireless power receiver 100 b power output circuitry'spower output to not exceed a maximum limit and by monitoring, computingand reconfiguring this maximum output power limit in the early period ofpower transfer to adjust for alignment conditions, operatingefficiencies, etc.

During stable power transfer from the wireless power transmitter 100 ato one or more wireless power receivers 100 b, one or more wirelesspower receivers 100 b may be placed within or removed from the chargingzone of the wireless power transmitter 100 a. As disclosed herein,charging zone is the area in the vicinity of wireless power transmitter100 a within which wireless power receiver 100 b if placed, canwirelessly receive power from this wireless power transmitter 100 a.Removal of one or more wireless power receivers 100 b from the chargingzone of the wireless power transmitter 100 a would make available moreof the power from the input power source to the wireless power receivers100 b that are still in the charging zone. For example, if the inputpower source has a maximum power availability of 10 W and if itdistributes that power equally to two wireless power receivers 100 bthat are in the charging zone, then when one of the wireless powerreceivers 100 b is removed from the charging zone, the full 10 W ofpower from the input source can now be made available to the wirelesspower receiver 100 b that is still in the charging zone. In the wirelesspower system disclosed herein, the wireless power transmitter 100 asenses the removal of one or more wireless power receivers 100 b fromthe charging zone, recalculates the power distribution among thewireless power receivers 100 b that are in the charging zone and sendsinformation message to them for the wireless power receivers 100 b toupdate their respective maximum output power limits. As a result, thewireless power receiver 100 b can deliver more power to the load if theload so requires. As the maximum output power limits are beingincreased, it is not necessary to halt the power transfer eventemporarily.

Addition of one or more wireless power receivers 100 b into the chargingzone of the wireless power transmitter 100 a would make available lessof the power from the input source to the wireless power receivers 100 bthat were already in the charging zone. For example, if the input sourcehas a maximum power availability of 10 W and if it is providing thatpower to one wireless power receiver 100 b that is in the charging zone,then when a second wireless power receiver 100 b is placed inside thecharging zone of wireless power transmitter 100 a, the full 10 W ofpower from the input source has to be shared by both wireless powerreceivers 100 b and will not be available entirely to the first wirelesspower receiver 100 b. If the load of this first wireless power receiver100 b was drawing power at the configured maximum power limit, then inall likelihood, on the addition of the second wireless power receiver100 b into the charging zone, the first wireless power receiver 100 bwill no longer be able to deliver the power drawn by its load. Thiscauses instability of power transfer between the wireless powertransmitter 100 a and the wireless power receivers 100 b.

In the wireless power system disclosed herein, the wireless powertransmitter 100 a senses the insertion of one or more wireless powerreceivers 100 b into the charging zone. It then takes suitable action toensure that the stability of power transfer remains uncompromised. Inthe first embodiment, the wireless power transmitter 100 a does notallocate all the available power from the input source to the one ormore wireless power receivers 100 b that are currently being charged. Itretains a small amount of power and provides this retained power to thenewly added one or more wireless power receivers 100 b only. With thissmall amount of power, the newly added wireless power receivers 100 bcan power up and communicate their needs to the wireless powertransmitter 100 a without affecting the ongoing power transfer to otherpreviously placed wireless power receivers 100 b. With awareness of themaximum available power from the input source and the maximum requiredpower from each of the wireless power receivers 100 b, the wirelesspower transmitter 100 a recalculates the power distributionconfiguration among the wireless power receivers 100 b in the chargingzone. The wireless power transmitter 100 a sends a “renegotiate” messageto the wireless power receivers 100 b that are in the charging zonecausing them to interrupt their power transfer to their loads. Thesewireless power receivers 100 b will then share their information againand renegotiate new power transfer contracts with the wireless powertransmitter 100 a. Based on the recomputed power distributionconfiguration, the wireless power transmitter 100 a sends informationmessage to the wireless power receivers 100 b and the wireless powerreceivers 100 b configure their maximum power output limit to align withthis new redistributed power configuration.

In a second embodiment, the wireless power transmitter 100 a hasallocated all the available power from the input power source to the oneor more wireless power receivers 100 b that are currently being chargedso when the wireless power transmitter 100 a senses the insertion ofadditional wireless power receivers 100 b into the charging zone, itmomentarily terminates the power transfer to all the wireless powerreceivers 100 b. The stop and restart of power causes the wireless powerreceivers 100 b to reset, interrupt their power transfer to theirrespective loads, share their information again and renegotiate newpower transfer contracts with the wireless power transmitter 100 a. Withawareness of the maximum available power from the input source and themaximum required power from each of the wireless power receivers 100 b,the wireless power transmitter 100 a recalculates the power distributionconfiguration among the wireless power receivers 100 b in the chargingzone. The wireless power transmitter 100 a then sends informationmessage to the wireless power receivers 100 b and the wireless powerreceivers 100 b configure their maximum power output limit to align withthis new redistributed power configuration.

In a third embodiment, when the wireless power transmitter 100 a sensesthe insertion of one or more wireless power receivers 100 b into thecharging zone, upon realizing that the power transfer will becomeunstable, the wireless power transmitter 100 a sends a “renegotiate”message to the wireless power receivers 100 b that were already in thecharging zone causing them to interrupt their power transfer to theirloads. These wireless power receivers 100 b will then share theirinformation again and renegotiate new power transfer contracts with thewireless power transmitter 100 a. With awareness of the maximumavailable power from the input source and the maximum required powerfrom each of the wireless power receivers 100 b, the wireless powertransmitter 100 a recalculates the power distribution configurationamong the wireless power receivers 100 b in the charging zone. Thewireless power transmitter 100 a then sends information message to thewireless power receiver 100 b and the wireless power receivers 100 bconfigure their maximum power output limit to align with this newredistributed power configuration.

In a fourth embodiment, when the wireless power transmitter 100 a sensesthe insertion of one or more wireless power receivers 100 b into thecharging zone, the wireless power transmitter 100 a opportunisticallyprovides the required power to the newly added wireless power receivers100 b. Based on their current power delivery, the previously placedwireless power receivers 100 b may notice immediately or in due courseof time, a drop in the negotiated guaranteed maximum power delivery. Theinability to deliver at the negotiated guaranteed maximum power deliveryleads to instability so wireless power receiver 100 b sendsrenegotiation messages to the wireless power transmitter 100 a. Asexplained, the wireless power transmitter 100 a recalculates the powerdistribution configuration among the wireless power receivers 100 b inthe charging zone. The wireless power transmitter 100 a then sendsinformation message to the wireless power receiver 100 b. Based on thesemessages, the wireless power receiver 100 b reconfigures its maximumoutput power limit leading to stable power transfer to its load. In anembodiment of the above, wireless power receiver 100 b monitors othervital operating parameters such as the external interface surfacetemperature, internal regulator temperature, etc. If any of theseoperating parameters were to cross their safe limits, the wireless powerreceiver 100 b uses the same mechanism to renegotiate the power transfercontract with the wireless power transmitter 100 a to help ensure thatthe power transfer is stable within prescribed safety operating limits.

When one or more wireless power receiver's 100 b are added to thecharging zone, the wireless power transmitter 100 a may partition anddistribute the available power from the input power source amongst thewireless power receivers in accordance with different criteria. In thefirst embodiment, the available power may be distributed equally amongstthe wireless power receivers. In the second embodiment, the availablepower may be distributed in proportion to the wireless power receiver's100 b respective maximum output power limit or other such wireless powerreceiver based generic criteria. In a third embodiment, the wirelesspower transmitter 100 a may choose to provide maximum power to one or afew select wireless power receivers 100 b while starving other wirelesspower receivers 100 b of any power delivery to their respective load.For example, if a wireless power receiver 100 b is added to the chargingzone of a wireless power transmitter 100 a that can provide a maximum of10 W of power, the wireless power transmitter 100 a may choose toprovide the full 10 W to this new wireless power receiver 100 b whilereconfiguring the previously charging wireless power receivers 100 b tonot deliver any power (0 W) to their respective loads. The criteria forpower distribution may be fixed or dynamic based on time of day, usercredentials, etc. In the wireless power system disclosed herein, thewireless power transmitter 100 a flexibly partitions and distributes theavailable power from the input power source to one or more wirelesspower receivers 100 b that are placed in its charging zone based on afixed or a dynamic algorithm.

In an embodiment of the wireless power system disclosed herein, thewireless power transmitter 100 a negotiates a new amount of availablepower from the input power source to accommodate the needs of one ormore wireless power receivers 100 b that are placed in the wirelesspower transmitter's 100 a charging zone. When one or more wireless powerreceivers 100 b are inserted into the charging zone, more input power isrequired to satisfy their needs so the wireless power transmitter 100 anegotiates for a higher amount of available power from the input powersource. When one or more wireless power receivers 100 b are removed fromthe charging zone, reduced amount of input power is required to satisfythe needs of the one or more wireless power receivers 100 b that arestill in the charging zone so the wireless power transmitter 100 anegotiates for a lower amount of available power from the input powersource. The wireless power transmitter 100 a may exchange messages withone or more input power source via industry standard protocol such asthe Universal Serial Bus Protocol Power Delivery (USB PD) specificationor via proprietary protocols such as the Qualcomm Quick Charge protocol,Samsung Fast Charge protocol, etc. Negotiating via such a protocol, thewireless power transmitter 100 a can increase or decrease the amount ofavailable power provided by the input power source so as to satisfy theneeds of the wireless power receivers 100 b that are situated in itscharging zone.

The foregoing examples have been provided merely for the purpose ofexplanation and are in no way to be construed as limiting of the presentinvention disclosed herein. While the invention has been described withreference to various embodiments, it is understood that the words, whichhave been used herein, are words of description and illustration, ratherthan words of limitation. Further, although the invention has beendescribed herein with reference to particular means, materials, andembodiments, the invention is not intended to be limited to theparticulars disclosed herein; rather, the invention extends to allfunctionally equivalent structures, methods and uses, such as are withinthe scope of the appended claims. Those skilled in the art, having thebenefit of the teachings of this specification, may affect numerousmodifications thereto and changes may be made without departing from thescope and spirit of the invention in its aspects.

I claim:
 1. A wireless power system comprising: a wireless powertransmitter operatively connected to an input power source, saidwireless power transmitter configured to deliver power from said inputpower source wirelessly to one or more wireless power receivers that areplaced within its charging zone one or more said wireless powerreceivers configured to receive power wirelessly, said wireless powerreceivers configured to deliver said received power to their respectiveload wherein said wireless power transmitter performs one or more of:sensing the removal of one or more said wireless power receivers fromits said charging zone and taking appropriate action in conjunction withsaid wireless power receivers that are still within its said chargingzone to ensure that said transfer of power to said load of said wirelesspower receivers that are still within its said charging zone remainsstable. sensing the insertion of one or more newly placed wireless powerreceivers into its said charging zone and taking appropriate action inconjunction with said wireless power receivers that are in its saidcharging zone to ensure that said transfer of power to said load of allsaid wireless power receivers that are within its said charging zone isstable.
 2. A wireless power system comprising: a wireless powertransmitter operatively connected to an input power source, saidwireless power transmitter configured to deliver power from said inputpower source wirelessly to one or more wireless power receivers that areplaced within its charging zone one or more said wireless powerreceivers configured to receive power wirelessly, said wireless powerreceivers configured to deliver said received power to their respectiveload wherein said wireless power receiver senses violation of powertransfer contract that said wireless power receiver had previouslynegotiated with said wireless power transmitter in whose said chargingzone said wireless power receiver has been placed in, said wirelesspower receiver takes appropriate action in conjunction with saidwireless power transmitter to renegotiate a new said power transfercontract and update its circuitry to ensure that said transfer of powerto its said load is stable.
 3. The wireless power system of claim 2,wherein said wireless power receiver senses violation of guaranteedmaximum power delivery that said wireless power receiver had previouslynegotiated with said wireless power transmitter in whose said chargingzone said wireless power receiver has been placed in, said wirelesspower receiver takes appropriate action in conjunction with saidwireless power transmitter to renegotiate a new said guaranteed maximumpower delivery based on which said wireless power receiver updates itscircuitry to ensure that said transfer of power to its said load isstable.
 4. The wireless power system of claim 2, wherein said wirelesspower receiver senses violation of safety limits of its operatingparameters while receiving power from said wireless power transmitter inwhose said charging zone said wireless power receiver has been placedin, said wireless power receiver takes appropriate action in conjunctionwith said wireless power transmitter to renegotiate a new said powertransfer contract based on which said wireless power receiver updatesits circuitry to ensure that said transfer of wireless power to its saidload is stable and its said operating parameters do not violate theirsaid safety limits.
 5. The wireless power system of claim 1, whereinsaid wireless power transmitter flexibly partitions and distributes theavailable power from the input power source to one or more said wirelesspower receivers that are placed in its said charging zone based on oneof a fixed algorithm and a dynamic algorithm.
 6. The wireless powersystem of claim 2, wherein said wireless power transmitter flexiblypartitions and distributes the available power from the input powersource to one or more said wireless power receivers that are placed inits said charging zone based on one of a fixed algorithm and a dynamicalgorithm.
 7. The wireless power system of claim 1, wherein saidwireless power transmitter negotiates a new amount of available powerfrom said input power source to accommodate the needs of one or moresaid wireless power receivers that are in said wireless powertransmitter's charging zone.
 8. The wireless power system of claim 2,wherein said wireless power transmitter negotiates a new amount ofavailable power from said input power source to accommodate the needs ofone or more additional said wireless power receivers that are in saidwireless power transmitter's charging zone.
 9. A method for maintainingstability of power transfer from wireless power transmitter's inputpower source to load of wireless power receiver when one or more saidwireless power receivers are removed or inserted from charging zone ofsaid wireless power transmitter, said wireless power transmitterperforming one or more of: sensing removal of one or more said wirelesspower receivers from the said charging zone of said wireless powertransmitter, recalculating the power distribution configuration amongone or more said wireless power receivers that are still in the saidcharging zone of said wireless power transmitter and sending message tosaid wireless power receivers with information for said wireless powerreceivers to update their respective maximum output power limits ofpower delivery to their respective loads. sensing insertion of one ormore said wireless power receivers newly placed in the said chargingzone of said wireless power transmitter, receiving messages from thenewly placed said wireless power receivers, recalculating the powerdistribution configuration among said wireless power receivers that arein the said charging zone of said wireless power transmitter, sending arenegotiate message to one or more said wireless power receivers thatwere previously placed in the said charging zone of said wireless powertransmitter, receiving various information from previously placed saidwireless power receivers and sending message to said wireless powerreceivers with information for said wireless power receivers to updatetheir respective maximum output power limits of power delivery to theirrespective loads. sensing insertion of one or more said wireless powerreceivers into the said charging zone of said wireless powertransmitter, momentarily terminating said power transfer to all saidwireless power receivers, restarting power delivery to all said wirelesspower receivers, receiving various information from said wireless powerreceivers, recalculating the power distribution configuration among oneor more said wireless power receivers that are in the said charging zoneof said wireless power transmitter and sending message to said wirelesspower receivers with information for said wireless power receivers toupdate their respective maximum output power limits of power delivery totheir respective loads. sensing insertion of one or more said wirelesspower receivers newly placed in the said charging zone of said wirelesspower transmitter, receiving messages from the newly placed saidwireless power receivers, sending a renegotiate message to said wirelesspower receivers that had been previously placed in the said chargingzone of said wireless power transmitter, receiving various informationfrom previously placed said wireless power receivers, recalculating thepower distribution configuration among said wireless power receiversthat are in the said charging zone of said wireless power transmitter,and sending message to said wireless power receivers with informationfor said wireless power receivers to update their respective maximumoutput power limits of power delivery to their respective loads. saidwireless power receiver potentially performing: sensing violation ofpower transfer contract that said wireless power receiver had previouslynegotiated with said wireless power transmitter in whose said chargingzone said wireless power receiver has been placed in, sending arenegotiate message to said wireless power transmitter and sharing otherinformation needed to re-establish the power transfer contract,receiving message from said wireless power transmitter with informationfor said wireless power receiver to update its maximum output powerlimit for power delivery to said load.